Sharp DV-NC70U Service Manual - Page 29

8-18 A/C HEAD HEIGHT ROUGH ADJUSTMENT • Setting Azimuth screw Height screw Tilt screw Cassette tape DV-NC70U/C DV-NC72U 8-19 ADJUSTMENT OF TAPE DRIVE TRAIN 1. Tape run rough adjustment 1 Check and adjust the position of the tension pole. (See 8-14.) 2 Check and adjust the video search rewind back tension. (See 8-12.) 3 Connect the oscilloscope to the test point for PB ATR signal output (TP201). Set the synchronism of the oscilloscope to EXT. The PB ATR signal is to be triggered by the head switching pulse (TP202). 4 Set the alignment tape (VROATSV) to play. Guide roller Cassette Tape H Weight to prevent float (500g) Mechanism chassis Figure 8-25. 1. Set the cassette tape in the unit. 2. Press the PLAY button to put the unit in the playback mode. 3. Roughly adjust the height of the A/C head by turning the height screw until the tape is in the position shown below. A/C head Tape 0.3mm Figure 8-26. • Adjustment Adjust the height screw visually so that the control head is visible 0.3mm below the bottom of the tape. Figure 8-27. 5 Press the tracking button (+), (-) and change the ATR signal waveform from max to min and from min to max. At this time make sure that the ATR signal waveform changes nearly parallel. 6 Unless the ATR signal waveform changes nearly parallel, adjust the height of supply side and take-up side guide roller so that the envelope waveform changes nearly parallel. (For ATR signal adjustment procedure refer to Figure 8-31.) 7 Turn the tilt screw to remove the tape crease at the fixing guide flange. Playback the tape and check for tape crease at the fixing guide flange. (1) If there is no tape crease Turn the tilt screw clockwise so that tape crease appears once at the flange, and then return the tilt screw so that the crease disappears. (2) If there is tape crease Turn counterclockwise the tilt screw so that the tape crease disappears. (Reference) If the tilt screw is turned clockwise crease appears at the lower flange. 29